1. Field of the Invention
The present invention relates to an apparatus for intermittently feeding a predetermined amount or length of material such as a sheet or a rod to a working machine such as a press.
2. Description of the Prior Art
Such a material feeding apparatus has been known as having a first gripper device having a first fixed gripper and a first: movable gripper which cooperate with each other in clamping and unclamping a material therebetween, and a second gripper device carried by a slide block reciprocatingly movable along a predetermined path of feed of the material having a second fixed gripper and a second movable gripper which cooperate with each other in clamping and unclamping the material therebetween, wherein the clamping and unclamping operation of the first and the second gripper devices and the sliding motion of the slide block are effected in a timed relation by a suitable mechanism incorporating a cam and an oscillation arm, thereby feeding the material along the predetermined path. This type of material feeding apparatus is disclosed, for example, in Japanese Utility Model Publication No. 27549/1985 (KOKAI 60-27549).
This known apparatus, however involves the following problem due to the fact that both the first and the second movable grippers are controlled by means of a single oscillation arm operated by a single cam. Namely, it is difficult to design the apparatus to establish such a relation between the timing of operation of the first gripper device and the timing of operation of the second gripper device that both the first and the second gripper devices simultaneously grip the same piece of material at the beginning and at the end of each of the intermittent feeding cycles, thereby to attain a high precision of feed of the material.